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I need to replace part of an end joist. The joist sits (parallel) on a 2x4 cripple wall. How should the joint between old and new joist be handled?

As far as I can tell, California Residential Code chapter 5 just requires that the joist ends bear 1.5" minimum on wood support (R502.6), and that joists "framing from opposite sides over a bearing support shall lap not less than 3" and shall be nailed together with a minimum three 10d face nails" (R502.6.1).

The bearing part is easy--I can add a pair of 2x4 studs, or a 4x4 if required, to the cripple wall. But the 2 joist sections can't lap if they are in the original positions. I could easily add a 2nd sister joist next to the joint, and this sister could be as long as needed.

How would you handle this? Any input is appreciated!

  • yes, you can "sister" the joists together, but we'll need more info to help, like: span of joists, size of joists, spacing of joists, amount (length) of rot or deterioration in joist, load on joists (floor or roof above), bearing condition (is it on a pillar?) – Lee Sam Apr 28 '17 at 6:57
  • Hi, I rephrased the question--I added some details and removed others to clarify that I'm just asking about the connection between old and new joist section, and that the joist is the outermost parallel joist, sitting on a perimeter foundation cripple wall. THANKS! – Phil Esra Apr 28 '17 at 16:52
  • Are you replacing a rim joist? The code you cited doesn't apply there. Just butt them together and scab something on to keep them in position. Ideally you'll split on a common joist and you can fasten both ends to it. You don't need to add studs as the joist will span the gap easily. – isherwood Apr 28 '17 at 16:54
  • @isherwood: Is a "rim joist" perpendicular to the main row of joists? (I'm confused about that.) If so--no, this is not a rim joist, it is the last joist in the row of joists, sitting under an exterior wall. But if a rim joist is just a joist on the perimeter...yes, this is that (and therefore sounds like I've overcomplicated it!) – Phil Esra Apr 28 '17 at 17:07
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    Well, both sound like rim joists as they're carried by framing below. They don't really have a span. If that's the case, I'd patch it in with a few toenails and call it a day. – isherwood Apr 28 '17 at 17:17

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